<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

</body>
<script>
    const a  = {
        b : 1
    }

    a = {c : 1} // 报错
    a.b = 2; // 正确
</script>
</html>